This invention relates generally to sensors usable in vehicular applications, and more particularly, this invention relates to a steerable wheel angle sensor and mount.
Wheel angle signals from a wheel angle sensor may be employed by electronic data management to fine-tune power steering parameters, making driving easier and more enjoyable. In some vehicles, the wheels may be independently supported and steerable, and it may be necessary to have coordinated steering angles between front and rear wheels. Computer controls are able to resolve signals indicating steer angle differences, and make adjustments to the steering system as necessary, or, alternatively, provide different angles of certain wheels for various purposes.
In one prior system of measuring wheel angle in a vehicle, a power steering apparatus is provided with a steering shaft, which is rotated by manipulation of a steering wheel, and a valve unit coupled to the steering shaft. The valve unit supplies and drains hydraulic oil to and from a cylinder in accordance with rotation of the steering shaft. The cylinder has a pair of piston rods protruding from its sides and coupled to a vehicle wheel. The moving amount of the piston rods is detected by a stroke sensor, which is expensive. The angle of the wheels is computed based on the value detected by the stroke sensor, which complicates the computation of the wheel angle.
In another prior system of measuring wheel angle in a vehicle, linear movement of piston rods is converted into rotation by a converter, such as a link mechanism, and is detected by a potentiometer. The angle of the steered wheels is detected based on the value detected by the potentiometer. The use of a converter increases the number of parts and complicates the installation of the apparatus. If the converter is not assembled accurately, the detection of the wheel angle will be inaccurate.
Current wheel angle sensors for electric power steering systems, which eliminate the need for the power steering pump and hydraulic fluid, and four wheel steering systems measure the pinion angle or the rack position. In one example, the sensor is positioned at the bottom of the actuator and additional costs are associated with protecting the sensor from ground clearance and jacking issues.
One problem with measuring a steered wheel angle is that the wheels and the steered wheel axis are potentially subject to harsh environmental conditions. This makes locating measurement systems or sensors difficult. Environmental conditions such as dirt or water can adversely impact the accuracy of sensor measurements or damage sensors. Prior wheel angle sensors, which are located so as to be protected from environmental damage, have been difficult to reach for maintenance and repair purposes.